1. Ruminant Animals
Ruminant animals are mammals of the suborder Ruminantia that have a stomach divided into four compartments: the rumen, the reticulum, the omasum, and the abomasum. Bacteria present in the rumen enable ruminants to digest cellulosic materials such as grass. Conventional digestion occurs in the abomasum, sometimes called the “true stomach.” Well-known ruminants include cattle, sheep, and goats.
A wide variety of supplements are known to improve milk production and weight gain in cattle and other ruminants. Many of these supplements are most effective only if they reach the abomasum of the animal. Unfortunately, the bacteria in the rumen are adversely affected by some of these supplements. Other supplements do not affect the rumen bacteria, but are chemically transformed or otherwise adversely affected themselves by the conditions in the rumen. Accordingly, it is common to “protect” the supplements in such a way that they bypass the rumen.
2. Fats
Fats are low cost, high energy foods that are commonly fed as supplements to cattle and other ruminants. The term “oil” is sometimes used for fats that are liquid at room temperature. The two terms are used interchangeably herein. Fats are substances of plant or animal origin that consist primarily of triglycerides. A triglyceride is produced in the condensation reaction of one molecule of glycerol with three molecules of fatty acids: where R, R′, and R″ represent fatty acid radicals. A fatty acid is an aliphatic compound containing 4 to 24 carbon atoms and having a terminal carboxyl radical. Naturally occurring fats contain small quantities of other compounds, including free fatty acids and glycerol. Fats are frequently refined to remove these compounds. The term “fat” is used herein to refer to triglycerides and/or free fatty acids, as the context requires.
Naturally occurring fatty acids, with only minor exceptions, have an even number of carbon atoms and, if any unsaturation is present, the first double bond is generally located between the ninth and tenth carbon atoms. Fatty acids are sometimes abbreviated by listing their number of carbon atoms and their number of double bonds. Some of the more common fatty acids in naturally occurring fats are listed in Tables 1 and 2.
TABLE 1SATURATED FATTY ACIDSCommon NameAbbreviationFormulaCaprylic 8:0C8OOHCapric10:0C10OOHLauric12:0C12OOHMyristic14:0C14OOHPalmitic16:0C16OOHStearic18:0C18OOH
TABLE 2UNSATURATED FATTY ACIDSCommon NameAbbreviationFormulaCaproleic10:1C═C9OOHLauroleic12:1C3═C9OOHOleic18:1C9═C9OOHLinoleic18:2C6═C3═C9OOHLinolenic18:3C3═C3═C3═C9OOH
The distribution of the different fatty acid radicals vary among naturally occurring fats. For example, the distribution of fatty acid radicals in soybean oil triglycerides is about 55% linoleic, 22% oleic, 11% palmitic, 8% linolenic, 3% stearic, and 1% other. Thus, soybean oil has an unsaturation level of about 85% (i.e., it has about 85% unsaturated fatty acids and about 15% saturated fatty acids). The distribution of free fatty acids is the same as the distribution of fatty acid radicals in the triglycerides.
Unsaturated fatty acids are known to be more digestible and are more beneficial after digestion to animals (and humans) than saturated fatty acids. An unsaturated fatty acid also has a lower melting point than a saturated fatty acid of the same number of carbon atoms. For example, animal fats have a relatively high percentage of saturated fatty acids and are typically solids at room temperature. In contrast, vegetable oils have a relatively high percentage of unsaturated fatty acids and are typically liquids at room temperature.
3. Rumen Bypass Supplements Containing Fat
Fats can adversely affect the digestion of cellulosic food in the rumen if they constitute too high a percentage of the food. It has been theorized that the adverse effect is due to several factors, including the following: (1) fats physically coat the cellulosic food which hinders the rumen bacteria in reaching the food; (2) fats, especially unsaturated fats, directly cause harm to the rumen bacteria; and (3) fats change the pH in the rumen in a way that indirectly harms the rumen bacteria.
One widely used method of increasing fat in the diet of a ruminant without adversely affecting the rumen bacteria is to include salts of fatty acids in the diet. Palmquist, U.S. Pat. No. 4,642,317, issued Feb. 10, 1987, discloses the use of calcium salts of fatty acids as a diet supplement for ruminants. The calcium salts pass through the rumen with little degradation. Accordingly, such supplements are commonly known as rumen bypasses. The calcium salts are formed by reacting fatty acids with calcium oxide (lime): 
The salt formation reaction is spontaneous (no catalyst is required) and is highly exothermic (it produces heat). The reaction is typically conducted by adding a suspension of calcium oxide in water to a liquid source of fatty acids and then stirring the reaction mixture rapidly. The reaction mixture hardens as the salt is formed. The resulting product is cooled and then ground into small particles.
Theoretically, the salt formation reaction goes to completion. In other words, all the fatty acid and/or all the metal is completely reacted. However, in practice, the salt formation reaction does not go to completion. One theory is that the reaction mixture hardens before all the reactants can reach each other.
A variety of reactants are used to make rumen bypass fat supplements. Metals other than calcium, such as magnesium and other Group II elements, are suitable. However, calcium compounds are generally used because they are more readily available and less expensive. A variety of fatty acid sources are used. Preferred fatty acid sources are by-products consisting primarily of free fatty acids that are removed from naturally occurring fats. These by-products are generally less expensive than the refined fats. For example, soybean soapstock consists of free fatty acids separated from crude soybean oil. Palm fatty acid distillate consists of free fatty acids distilled from crude palm oil. Beef tallow acids are free fatty acids derived from waste beef fat.
As previously mentioned, there are nutritional benefits in using a source of fatty acids with a high percentage of unsaturation. However, because the salt formation reaction generally does not go to completion, an amount of unreacted unsaturated free fatty acids remain in the product. This creates two problems. First, the unsaturated free fatty acids have relatively low melting points and make the resulting product unacceptably soft in texture. Secondly, the unreacted fatty acids continue to slowly react after the product is produced which, in turn, creates heat. To reduce these two problems, it is common practice to add saturated fats to the reaction mixture if a fatty acid source having a high level of unsaturation is used. Accordingly, rumen bypass fat supplements typically have an unsaturation level of less than about 50%. This somewhat defeats the purpose of using a fatty acid source having a high level of unsaturation.
Vinci et al., U.S. Pat. No. 5,182,126, issued Jan. 26, 1993, discloses a rumen bypass fat supplement that contains various micronutrients. The supplement is prepared by reacting fatty acids with an alkaline earth metal compound. Vinci et al. state that optional ingredients such as antioxidants, preservatives, and surfactants can be incorporated in the process. Suitable surfactants are nonionic surfactants, hydrocolloids, and cellulose ethers.
4. Choline
Choline is a micronutrient that improves milk production due to its effect on nerve tissue and fat metabolism: Choline also helps transition (prepartum) cattle avoid the “fatty liver” problem that can cause poor milk production and decrease fertility. Choline chloride contains a chlorine atom in place of the hydroxyl group attached to the nitrogen atom. Choline chloride has the same biological function as choline. Another choline derivative with a similar biological function is phosphatidyl choline: where R and R′ are fatty acid groups. Crude soybean lecithin, a by-product of the soybean oil refining process that is commonly used as an emulsifier, typically contains about 15 to 20 percent phosphatidyl choline.
5. Rumen Bypass Supplements Containing Choline
Choline is rapidly metabolized by the bacteria present in the rumen. One widely used method of protecting choline is to encapsulate it in a solid fat. Blagdon et al., U.S. Pat. No. 5,496,571, issued Mar. 5, 1996, discloses a method of encapsulating choline to produce a rumen bypass supplement for ruminants. This type of encapsulation produces spherical particles having a core of choline surrounded by a shell of fat. Encapsulation is a relatively expensive manufacturing process. Furthermore, the high degree of saturation of the fat needed for solidification tends to reduce the digestibility of the choline.
Ueda et al., U.S. Pat. No. 5,227,166, issued Jul. 13, 1993, discloses a feed supplement for ruminants consisting of a coated biologically active substance, such as an amino acid, drug, or vitamin. The coating is made from a hardened oil or wax with 0.1 to 10 weight percent of an inorganic substance such as magnesium carbonate and with about 0.1 to 20 weight percent lecithin. Ueda et al. teach that the lecithin is present in the coating to provide emulsification. Ueda et al. state that the coating remains intact in the rumen but dissolves in the acidic environment of the abomasum. The amount of the inorganic substance is so small relative to the oil that little reaction occurs.
6. Rumen Bypass Supplements Containing Fat and Choline
Attempts have been made to incorporate choline into conventional rumen bypass fat supplements. However, it was discovered that choline is broken down during the conventional salt formation reaction. For example, Vinci et al. U.S. Pat. No. 5,456,927, issued Oct. 10, 1995, discloses a feed supplement for ruminants consisting of a fatty acid calcium salt containing a biologically active ingredient. Vinci et al. teach that “the selection of the biologically active ingredient is restricted because many important nutrient compounds . . . do not survive the calcium oxide hydration and fatty acid salt-formation exothermic reaction conditions which are inherent in the invention process embodiments. Nutrient compounds such as . . . choline are chemically transformed under the exothermic reaction conditions characteristic of the invention process.”
Accordingly, there is a demand for an improved rumen bypass fat supplement and there is an especially great demand for one that contains both fat and choline.